Such centrifugal force sliding grinding machines, e.g. for the final treatment of bulk items such as screws, needles or articles of jewellery are known and used in large numbers. A base part forming the bottom of the container rotates with respect to a stationary container part, so that there is a relative movement between these two parts, which leads to a corresponding rotationally symmetrical flow in the container. The two parts are conventionally separated from one another by an annular clearance or annular gap, in order on the one hand to avoid wear between the two parts moved relative to one another and also for conducting working fluid into the container, particularly in the case of wet machining. The working fluid is introduced into the container in that a storage area is provided, which is supplied with working fluid at a predetermined pressure, so that said fluid can be brought into the container. It is removed from there by means of a central drain in the vicinity of the base part. Attempts have admittedly already been made to ensure that the gap is as small as possible, so that grinding or polishing materials are not pressed outwards by the rotary movement through the gap, but a gap of at least approximately 0.2 to 0.5 mm is still necessary, so that no thin workpieces can be machined, workpieces are damaged by jamming in the gap and the grinding and polishing article must drop below a certain size.
An introduction of such grinding or polishing materials into the gap leads to wear both to the stationary container part and to the base part, which can evolve progressively with increasing gap width, because with increasing wear ever larger particles enter the gap and simultaneously have grinding effects on both gap faces. To reduce this wear in the gap and therefore increase the service life of the base part, it is e.g. known to vary the gap width by a central gap arrangement means located at the drive shaft of the base part (DE 43 11 689 A1). However, such a gap adjustment requires the maintaining of close tolerances in the area of the thrust bearing clearance of the drive shaft and is consequently expensive.
DE 195 42 541 discloses a centrifugal force sliding grinding machine, whose gap is closed under the action of an elastic means, such as a sliding packing, sealing lip or spring, so that the passage of working fluid during wet machining is determined as a function of the pressure thereof against the force of the elastic means determines the gap width. However, it is disadvantageous in such a centrifugal force sliding grinding machine that the annular gap both during dry machining and when machining bulk items, whose diameter is large compared with the gap width, so that no container wear can take place through bulk material penetrating the gap, is closed by the elastic means, so that the latter sliding along the rotating base part is subject to constant wear and the drive motor of the base part constantly starts up against a frictional resistance.